1. Field of the Invention
This application relates to marine VHF radio antennas. More particularly, it concerns novel type of antennas that can be used with marine hand held transceivers operating in the VHF band and particularly aboard sailboats.
2. Description of the Prior Art
A typical VHF radio installation on a sailboat consists of a quarter wave whip mounted on top of the sailboat's mast. A long length of low impedance coaxial cable runs down through the mast and connects the antenna to the ship's VHF radio. This arrangement provides the greatest transmitting and receiving range since VHF transmission is largely line of sight. The power level of marine VHF transceivers is typically 25 watts, the maximum allowed by the FCC.
There are several disadvantages inherent in mast mounted antenna systems. These include (a) changes in antenna pattern and concomitant changes in range that occur with roll, heel and pitch, (b) need to go to the top of the mast to affect repairs to the antenna, (c) loss of communications in the case of catastrophic mast failure, (d) permanent installation that is not movable from boat to boat, (e) difficulty of installation, particularly the coaxial lead inside the mast, and (f) need to remove the antenna at lay up.
Many mariners have augmented their primary ship's VHF radio with a hand held portable walkie-talkie type VHF radio. This type of radio is usually self contained and utilizes a telescoping or "rubber ducky" antenna that does not require any antenna installation on the boat. The FCC limits transmit power on such radios to 6 watts. These hand held radios have gained tremendous popularity recently due to their portability, but hand held radios suffer from an extremely short range, primarily as a result of the low height of the antenna.
Hand held transceivers also may involve a potential health risk due to RF exposure close to the users' head.
One might consider connecting a hand held radio to a mast-top mounted antenna, as a solution to many of the problems outlined here. A single mast-top antenna installation with a VHF switch between the primary radio and the hand held radio would allow use of either radio, but this solution is cumbersome. An alternate is the addition of a second permanently mounted antenna at mast-top, but this requires duplicate antennas and feedlines plus installation of a feedline to the cockpit where hand held radios are most often used.
Alternatively, one could hoist an antenna mounted to a length of coaxial cable up the ship's mast taking advantage of one of the ship's sail hoisting halyards. This is a temporary solution at best and will be noisy due to the slapping of the cable in the wind (leading to premature failure) and may interfere with the handling of the boat since it uses some of the boats primary equipment.
The present invention addresses the problems associated with prior known VHF marine radios and their antennas as discussed above and provides new improvements in VHF antennas that mitigate or entirely eliminate them.
The forestays and backstays of sailboats, in addition to acting as rigging for the mast, have been used in a variety of ways to provide columnar support to auxiliary items used aboard sailboats. Typically, the forestay provides support for the luffs of jib sails via snap-hanks. Recently, multi-grooved, elongated plastic extrusions have been used as clip-on leads to support jib luffs to the forestays in place of snap-hanks, e.g., see U.S. Pat. No. Re. 31,829.
As to backstays, a recent example of their use as vertical support for an auxiliary item aboard a sailboat is as a mount for a radar antenna, see U.S. Pat. No. 5,111,212.
The present invention utilizes the backstay of sailboats in an new manner to provide columnar support to its improved VHF radio antennas.